Is the farthest distance on the x and z axes 32,000,000? Or are the x and z axes 32,000,000 blocks long? Because if the farthest point on those axes is 32,000,000, that would make the total length of each axis 64,000,000 blocks long, because you could go to -32,000,000 blocks as well.

No. The volume of the sun is 1.412 quintillion km3. The volume of the MC world is 1.049 quintillion METERS3. A km3 is 1 000 000 000 m3. The ratio of the minecraft world's volume to the volume of the sun is then (1.049/1.412)/(10003 )~0.000 000 000 743, or roughly 743 parts per trillion. That is to say the Minecraft world is about 88% the volume of the earth's oceans, or roughly 20% the volume of Pluto.

Before beta 1.8 you used to theoretically be able to generate world infinitely in any direction, and the terrain and game mechanics would just become more and more glitchy once you went past the extremes. ("The farlands"). There technically would be a point where it became too glitchy to continue but that wasn't at a fixed spot. I think now there's just a fixed point which the game won't generate any terrain beyond.

If you stored only one integer per block, and each integer is 4 bytes long, 1.04*1018 bytes would be required. 953,674.31 Terabytes. I'm not sure how each block is stored in minecraft but my assumption is that they probably are represented with more than one int.

Secondly, even if its surface area were larger than Neptune, its volume would still be far lower. 9.216×1017 cubic meters is just .0851% (less than a tenth of a percent) of Earth's volume; a far cry from the 5700% implied by OP. MC's surface area is more than 7 times that of Earth's, but it's far, far shallower.

Well assuming each block is one byte (which is probably a horrible estimate, with metadata and entities and such the actual world will be way larger) the fully generated world will be over 260,000 terabytes. I was making the point that you don't ever see the whole world, that's just ridiculous. Your computer only stored the parts it has generated already and the information it needs to know how to generate the rest.

EDIT: I did make a bad estimate but it's still a massive amount of data.

On average, approximately 441 chunks per player, which is 28,901,376 blocks per player, which would be approximately 0.00000000275625% (roughly three one-hundred-millionths of a percent) of the total world's volume.

Could be more or less depending on server settings and/or draw distances. I used default values.

One byte for blocks (unless they are extended ids), one byte for light levels and block data, plus entities etc. and headers and biome data but also 16x16x16 blocks of air can be omitted, and files are compressed on the disk (albeit with it set to "speed" not "size")

Assuming a vanilla generated world, it wouldn't be ~ 1 byte per block. It's 12 bits per block, some blocks using more for entity, compressed with deflate. You can safely assume on average 96 and above will usually be air, which isn't stored in anvil. Thus, you come up with 96 * 16 * 16 = 24576 blocks per chunk, or 36864 bytes per chunk. Deflate on heavily monotonous data such as minecraft chunks can probably get this down to 4 kilobytes (minimum chunk size in minecraft if I recall correctly, don't quote me). Realistically, you're looking at about 60 pebibytes (base1024). For comparison, that's about 1400 XS29's at Hetzner (assuming no redundancy).

My mistake, I didn't account for negative coordinates. The longest distance on both the x and z axis would be 64 million, with 32 million one way and 32 million the other way (negative) So, the correct volume of minecraft would indeed be four times as big as what I said in the post, making Minecraft even more massive. My apologies for the bad math.

I would enjoy some more comparisons proceeding the volume conclusion. For example, I did a little research and learned that Minecraft's volume is approximately 206,738 times larger than the Pacific, Atlantic, Indian, and Arctic oceans combined.

The Nether is exactly the same size as the overworld. You just can't use portals there past 3,750,000, or it'll crash the game, because it's trying to return you to the overworld past 30,000,000, where chunks don't exist.

Bonus: If you multiply that number by number of all different blocks that could be placed into world (including their metadata like direction of lever or height of snow layer) + 1 (since there is also possibility that the block won't be occupied at all), you'll get number of all different Minecraft universes (excluding entities), which ever were, are and will be built. I once calculated that, but back then the newest blocks were beacon ones, so you get idea how outdated that is...

Yes, your finished project is there somewhere, you have just to work on it, so chop chop!

Bonus: If you multiply that number by number of all different blocks that could be placed into world (including their metadata like direction of lever or height of snow layer) + 1 (since there is also possibility that the block won't be occupied at all), you'll get number of all different Minecraft universes (excluding entities), which ever were, are and will be built.

No, that is not how it works. It would be number of all different blocks to the power of that number. Which is mind boggingly huge.

Wait, so you could build a 1:1 scale earth at least in a 2d projection in one minecraft world? I know the height would have to scale somewhere between 35-75m per block depending on whether you go down to the bottom of the ocean or not, but a flat projection should otherwise fit in x,y space. Is there an practical limit on file size of the world before the game stops functioning?

The nether is 1/8th the size of the overworld, and the same height limit (although it only generates terrain up to y=128). So based on the volume in this comment the amount of space in the nether is 1.31072x1017 or 131,072,000,000,000,000 blocks.

The Nether is not really located beneath the overworld, but rather in a different dimension. Technically the nether is a different version of the world. Also any distance covered in The Nether is multiplied by 8, which probably mean it is about 1/8th in max theoretical size.